1. Field of the Invention
The present invention relates generally to an improved rear sole for footwear and, more particularly, to a rear sole for an athletic shoe with an extended and more versatile life and better performance in terms of cushioning and spring.
2. Discussion of the Related Art
Athletic shoes, such as those designed for running, tennis, basketball, cross-training, hiking, walking, and other forms of exercise, typically include a laminated sole attached to a soft and pliable upper. The laminated sole generally includes a resilient rubber outsole attached to a more resilient midsole usually made of polyurethane, ethylene vinyl acetate (EVA), or a rubber compound. When laminated, the sole is attached to the upper as a one-piece structure, with the rear sole being integral with the forward sole.
One of the principal problems associated with athletic shoes is outsole wear. A user rarely has a choice of running surfaces, and asphalt and other abrasive surfaces take a tremendous toll on the outsole. This problem is exacerbated by the fact that most pronounced outsole wear, on running shoes in particular, occurs principally in two places: the outer periphery of the heel and the ball of the foot, with peripheral heel wear being, by far, a more acute problem. In fact, the heel typically wears out much faster than the rest of a running shoe, thus requiring replacement of the entire shoe even though the bulk of the shoe is still in satisfactory condition.
Midsole compression, particularly in the case of athletic shoes, is another acute problem. As previously noted, the midsole is generally made of a resilient material to provide cushioning for the user. However, after repeated use, the midsole becomes compressed due to the large forces exerted on it, thereby causing it to lose its cushioning effect. Midsole compression is the worst in the heel area, including the area directly under the user's heel bone and the area directly above the peripheral outsole wear spot.
Despite technological advancements in recent years in midsole design and construction, the benefits of such advancements can still be largely negated, particularly in the heel area, by two months of regular use. The problems become costly for the user since athletic shoes are becoming more expensive each year, with some top-of-the-line models priced at over $150.00 a pair. By contrast, with dress shoes, whose heels can be replaced at nominal cost over and over again, the heel area (midsole and outsole) of conventional athletic shoes cannot be. To date, there is nothing in the art that successfully addresses the problem of midsole compression in athletic shoes, and this problem remains especially severe in the heel area of such shoes.
Another problem is that purchasers of conventional athletic shoes cannot customize the cushioning or spring in the heel of a shoe to their own body weight, personal preference, or need. They are "stuck" with whatever a manufacturer happens to provide in their shoe size.
Finally, there appear to be relatively few, if any, footwear options available to those persons sufficing from foot or leg irregularities, foot or leg injuries, and legs of different lengths, among other things, where there is a need for the left and right rear soles to be of a different height and/or different cushioning or spring properties. Presently, such options appear to include only custom-made shoes that are prohibitively expensive and rendered useless if the person's condition improves or deteriorates.